1. Field of the Invention
The present invention relates to corrugated cardboard plates, a method of and an apparatus for making the corrugated cardboard plates from corrugated cardboards that are excellent in heat insulation and sound insulation, and have a lightweight feature and a strength. The present invention also relates to the corrugated cardboard plates and architectural elements utilizing the corrugated cardboard plates.
2. Description of the Prior Art
The assignee of the present invention has applied for patent on an apparatus for and a method of continuously manufacturing a honeycomb structure that can be used as a material for furniture and architectures (the Japanese Laid-open Patent Publication No. 11-235773). This honeycomb structure is lightweight and has cells exhibiting an extremely high compressive strength and is excellent in heat insulation and sound insulation. However, the apparatus for making the honeycomb structure tends to become somewhat complicated.
More specifically, the honeycomb structure is prepared by laminating a plurality of paper materials for forming honeycomb cells to provide a honeycomb core material, then forming honeycomb units by cutting the laminate of the paper materials in a direction perpendicular to the honeycomb cells while the latter are closed, successively connecting the honeycomb units, with upper and lower faces bonded together, to provide an elongated honeycomb core, and bonding a sheet to a cut face (front and rear sides) of the elongated honeycomb core to provide the honeycomb structure. However, at the time the honeycomb units are formed by cutting the honeycomb core material, a relatively large cutting force is required since the cutting is performed while the honeycomb cells are closed. For this reason, a guillotine cutter comprising a single knife blade and capable of exerting a higher cutting force than a saw tooth is employed for cutting the honeycomb core material. However, the use of the guillotine cutter results in a smooth cut face (a face where an adhesive is to be applied) and, therefore, the adhesive applied will not be satisfactorily retained on the cut faces of the honeycomb units, with the consequence that the sheet will not be firmly bonded to the elongated honeycomb core. In view of this, while the cells of the honeycomb units are expanded by the use of an expander, the front and rear faces of each honeycomb units where the adhesive is to be subsequently applied is roughened by the use of a surface roughening device. As such, the manufacture of the honeycomb structure requires the use of the surface roughening device and the expander.
The present invention is intended to provide corrugated cardboard plates at a reduced cost, wherein corrugated cardboards are employed in place of the above discussed honeycomb core materials, wherein the sheet can be assuredly and firmly bonded with no surface roughening being required, and which has a performance comparable or higher than that exhibited when the honeycomb core materials are used.
Another important object of the present invention is to provide an architectural material wherein the corrugated cardboard plates are used so that it can be suitably and optimally used as a floor panel, a partition wall for use in restaurants and offices or an external wall for a temporary dwelling, all of which have an excellent lightweight feature and an excellent thermal insulation.
In order to accomplish these objects of the present invention, a method of making corrugated cardboard plates according to the present invention includes a step of laminating and bonding a plurality of corrugated cardboards to provide a corrugated cardboard laminate, each of the corrugated cardboards including a corrugated sheet and at least one liner sheet bonded to the corrugated sheet, the corrugated sheet having a plurality of cells and a corresponding number of ridges; a step of cutting the corrugated cardboard laminate along a plurality of cutting lines lying perpendicular to a direction in which the ridges of the corrugated sheet extend, to provide a plurality of corrugated blocks, each of the corrugated blocks having upper and lower faces opposite to each other; a step of arraying the corrugated blocks in a line to provide an elongated flat corrugated plank in which the top face of one of the corrugated blocks is bonded to the bottom face of the next adjoining corrugated block; a step of bonding at least one backing sheet, made of paper, to one of opposite surfaces of the elongated flat corrugated plank; and a step of cutting the elongated flat corrugated plank into a plurality of corrugated cardboard plates of a predetermined size. The corrugated sheet referred to above is a sheet corrugated at regular intervals so that cells can be formed in the corrugated cardboard, which cells may have a generally U-shaped (or sinusoidal) section, a generally V-shaped section or a trapezoidal section.
With the above described corrugated cardboard plate making method, when the corrugated cardboard laminate is to be cut along cutting lines lying perpendicular to ridge lines of the corrugated sheet into a plurality of corrugated blocks, not a guillotine cutter including a single knife blade, but a circular saw or a band saw including a body having its tip formed with rows of equally spaced saw teeth or a so-called raking saw having a plurality of equally spaced saw teeth that are alternately offset laterally relative to each other to provide two rows of alternating saw teeth, can advantageously be employed. In other words, since the corrugated cardboard laminate is of a design wherein corrugated cardboards are laminated together with the cells left open and does not require a relatively large force during the cutting thereof, the use of the circular saw, the band saw or the ranking saw is possible. For this reason, cut faces of each of the corrugated cardboard blocks resulting from cutting of the corrugated cardboard laminate can be suitably roughened and, therefore, by applying an adhesive to the cut faces of each of the corrugated cardboard blocks optimally, the sheet can be assuredly and firmly bonded. Accordingly, no surface roughening need not be performed with the use of the surface roughening device and the expander such as required in the previously suggested apparatus. Accordingly, it is possible to continuously manufacture at a reduced cost the corrugated cardboard plates having excellent heat and sound insulations and being lightweight and robust and, yet, capable of exhibiting a performance comparable to or higher than that exhibited by the use of the honeycomb core material.
An apparatus for making corrugated cardboard plates according to the present invention includes a laminating machine for making a corrugated cardboard laminate by laminating and bonding a plurality of corrugated cardboards, each of the corrugated cardboards including a corrugated sheet and at least one liner sheet bonded to the corrugated sheet, the corrugated sheet having a plurality of cells and a corresponding number of ridges; a corrugated block former for making a plurality of corrugated blocks by cutting the corrugated cardboard laminate along a plurality of cutting lines lying perpendicular to a direction in which the ridges of the corrugated sheet extend, each of the corrugated blocks having upper and lower faces opposite to each other; a corrugated plank preformer for making an elongated flat corrugated plank by arraying the corrugated blocks in a line, in which the top face of one of the corrugated blocks is bonded to the bottom face of the next adjoining corrugated block; a corrugated plank former for making a continuous strip of corrugated plank by bonding at least one backing sheet, made of paper, to one of opposite surfaces of the elongated flat corrugated plank; and a corrugated plate former for cutting the elongated flat corrugated plank into a plurality of corrugated cardboard plates of a predetermined size.
The corrugated cardboard plate making method of the present invention can easily be practiced by the use of the corrugated cardboard plate making apparatus of the structure described above.
In a preferred embodiment of the present invention, during the formation of the corrugated blocks or in the corrugated block former performing the formation of the corrugated blocks, bent portions are formed at opposite ends of the corrugated sheet, that are positioned on front and rear sides thereof, so as to extend in a direction parallel to the front and rear sides by means of cutting performed by a cutter. The presence of these bent portions is effective to increase the physical strength of the corrugated sheet. Moreover, when the sheet is bonded to one or both of front and rear sides, the bonding surface area can increase because of the presence of the bent portions and, therefore, the bonding strength of the sheet can be increased.
A corrugated cardboard plate according to the present invention is the one manufactured by the method or the apparatus of the present invention. This corrugated cardboard plate is of a structure wherein a plurality of corrugated cardboards each including a corrugated sheet and at least one liner sheet bonded to the corrugated sheet are laminated and bonded together, said corrugated cardboard plate comprising the corrugated cardboards having front and rear sides thereof lying in a direction perpendicular to a direction conforming to ridges of the corrugated sheet.
The corrugated cardboard plate of the present invention is excellent in heat insulation and sound insulation and, also, lightweight and has a strength and, therefore, can be used as a floor panel, a partition wall, an external wall, a load bearing pallet, a core material for a table, a counter or a shelf, a core material for audio appliances or office automation appliances, a cushioning material for packages, a corner member for packaging, or a filter when filled with a mass of titanium oxide or activated carbon particles, or an element for a heat exchanger. Thus, the corrugated cardboard plate of the present invention can find a variety of applications.
In a preferred embodiment of the present invention, the corrugated sheet forming the corrugated cardboard plate has end portions positioned on the front and rear sides, respectively, and bent in a direction conforming to the front and rear sides thereof.
In another preferred embodiment of the present invention, each of the bent portions has a length within the range of 1.0 to 5.0 times the thickness of the corrugated sheet. By so doing, the physical strength of the corrugated cardboard plate can be increased and bonding of the sheet to the bent portions can be assuredly achieved. At this time, if the length of each of the bent portions is chosen to be of a value smaller than 1.0 times the thickness of the corrugated sheet, no sufficient physical strength can be obtained and no sufficient bonding of the sheet can also be obtained. On the other hand, if the length of each bent portion is chosen to be of a value greater than 5.0 times the thickness of the corrugated sheet, no simplified and efficient formation of the bent portions is possible. In other words, the corrugated cardboard plate is prepared by cutting corrugated cardboard laminates into a plurality of corrugated cardboard blocks by the use of a saw, which blocks are in turn connected together with upper and lower faces thereof bonded with each other. Therefore, if the bent portions are formed by the utilization of margins left at the cut ends of each of the corrugated cardboard block at the time of cutting by means of the saw, no separate manufacturing step is required and the bent portions can advantageously be formed simultaneously with the cutting. However, if the length of each of the bent portions exceeds a value greater than 5.0 times the thickness of the corrugated sheet, simultaneous formation of the bent portions with the cutting saw will become difficult. Accordingly, in order for the bent portions to be formed efficiently by the utilization of the manufacturing step of the corrugated cardboard plates, the length of each of the bent portion should be within the specific range as described above. Also, since the corrugated cardboard plate of the structure described above is excellent particularly in physical strength, it can be optimally utilized when used as material for the load bearing pallet, the furniture or the core material for the rack.
In a further preferred embodiment of the present invention, the corrugated sheet has cells of a height within the range of 5 to 15 mm. If the cells in the corrugated sheet has a height within this range, a relatively small number of the corrugated cardboard is sufficient to provide the corrugated cardboard plate of a predetermined size. In other words, since the height of the cells in the standard corrugated cardboard is generally within the range of 1.1 to 4.8 mm, a relatively large number of the standard corrugated cardboards is required to produce the corrugated cardboard plate of a predetermined size and results in increase of the weight of the resultant corrugated cardboard plate. Also, from the standpoint of saving of the limited resources, it is problematic. However, if the corrugated cardboards having a relatively large cell height as discussed above, which is generally referred to as xe2x80x9cOni Danxe2x80x9d or Big Cell Corrugate, is used, a relatively small number of the corrugated cardboards is sufficient to produce the corrugated cardboard plate of a predetermined size. The corrugated cardboard plate so manufactured is lightweight and resource-saving and, yet, brings about a favorable workability at the time of manufacture thereof. If the height of the cells in the corrugated sheet is smaller than 5 mm, a relatively large number of the corrugated cardboards would be required to produce the corrugated cardboard plate of a predetermined size as is the case with the standard corrugated cardboards. On the other hand, if the height of the cells in the corrugated cardboard is greater than 15 mm, it may result in reduction of the weight, but the strength will be insufficient. Accordingly, the height of the cells in the corrugated cardboard should be within the range specified above.